The present invention relates to a square-headed rivet fastener. Fasteners including a flange with a shaft extending therefrom-are well known. It is also well known to provide the shaft with an end remote from the flange having a reduced wall thickness to facilitate riveting that end over the surface of a piece of material through which the shaft has been inserted to hold the fastener against axial movement once riveted.
Applicant is aware of U.S. Pat. No. 5,348,432 to Nagayama that teaches a rivet-type tee nut having an octagonal flange with a shaft extending therefrom having a thicker-walled threaded portion adjacent the shaft and a thinner-walled unthreaded portion remote therefrom. In the Nagayama patent, two pairs of pawls are provided and are interconnected together by respective linear edges of the flange.
The concept of a tee nut having an octagonal flange in which pairs of pawls are interconnected by a linear edge was first developed by Sigma Tool and Machine as disclosed in U.S. Pat. No. 3,480,061 to Walter Leistner. The tee nut disclosed and claimed in the ""061 patent was designed to permit it to be guided both as a tee nut blank to the station where it would be tapped, and as a completed tee nut to a location where it would be inserted. The linear edge between the pair of pawls was devised to permit adjacent tee nuts in the track (or tee nut blanks) to abut one another to preclude shingling, that is, overlapping of the flanges of adjacent tee nuts. When shingling occurs, the track becomes jammed and production must be stopped to un-jam the track.
In 1983, Sigma Tool and Machine developed an improved tee nut and obtained U.S. Pat. No. 4,508,478 to Herbert E. Leistner in 1985. The ""478 patent improved upon the ""061 patent by providing an inverted U-shaped abutment between the respective pairs of pawls, thereby rendering the edge therebetween non-linear and increasing the height of the abutment engaging an adjacent tee nut to significantly enhance protection against shingling.
In the ""061 patent and ""478 patent, tee nuts are disclosed as guided within the track by engagement of sides of the upraised pawls within a slot formed in the track. Tee nuts such as disclosed in Nagayama""s ""432 patent are guided in the track in the same manner.
A need has developed for a rivet-type fastener that may be guided within the track by the sides of the tee nut rather than by the pawls and wherein ribs are used to prevent shingling. Furthermore, a need has developed for a fastener wherein the fastener blank is formed in a forging operation with the fastener blank being subsequently tapped. A need has also developed for a fastener which may be guided in a track with the axis of elongation of the shaft thereof parallel to the direction of movement along the track rather than perpendicular to the direction of movement as is the case with tee nuts as disclosed in the ""061, ""478 and ""432 patents. It is with these needs in mind that the present invention was developed.
The present invention relates to a square-headed rivet fastener. The present invention includes the following interrelated objects, aspects and features:
(1) The present invention includes a generally square flange having arcuate corners. Eight upstanding ribs are provided, equally spaced about the periphery of the flange, each of which has a generally trapezoidal cross-section with sides tapering toward one another in the upward direction toward the shaft. When the inventive fastener is inserted in a piece of material such as, for example, a piece of wood, the ribs dig into a surface of the piece of wood to prevent the fastener from rotating when a threaded fastener is advanced into the opening through the shaft thereof from the opposite side.
(2) Each of the ribs is spaced from an adjacent rib by the combination of a linear edge and an arcuate edge of the flange. By xe2x80x9cedge,xe2x80x9d Applicant means the intersection between a top surface of the flange and a side wall thereof. Through the manufacturing process, there is no indentation formed in the bottom surface of the flange in a location aligned with each rib.
(3) Extending upwardly from the top surface of the flange is an elongated shaft that may, if desired, be generally cylindrical in outer configuration. It may also take on non-cylindrical shapes such as square or triangular cross-sectional shapes and shapes in which the diameter of the shaft varies along its length. At the end of the shaft distal from the flange, it is preferred that a tapered end be provided to best facilitate insertion of that end of the shaft within an opening in a piece of material. While the shaft has been described as generally cylindrical, in reality, the shaft must assume a slight taper from the flange to the end of the shaft distal from the flange so that, during the course of manufacture, the shaft can easily be removed from the die that is used to manufacture it.
(4) The shaft has two adjacent regions including a first region adjacent the flange having relatively thicker walls and an opening therethrough tapped with female threads. A second region distal from the flange has thinner walls and is unthreaded. If desired, a transition region may be provided between the first and second regions which comprises a generally frusto-conical surface diverging outwardly in the direction toward the distal end of the shaft. Of course, if desired, the wall thickness of the shaft may be made uniform substantially throughout its length.
(5) Where the passageway through the inventive fastener intersects with the bottom surface of the flange, the passageway may taper in a direction from the bottom surface of the flange toward the distal end of the shaft. This taper allows easy guidance of adjacent fasteners in a track in an embodiment where the track is configured to guide the fasteners with the axes of elongation of the shafts thereof aligned with the direction of movement through the track.
As such, it is a first object of the present invention to provide a square-headed rivet fastener.
It is a further object of the present invention to provide such a fastener in which upstanding trapezoidal cross-section ribs are employed to prevent shingling.
It is a still further object of the present invention to provide such a fastener including a generally cylindrical shaft with a tapered end to facilitate insertion of the fastener into an opening formed in a piece of material.
It is a still further object of the present invention to provide such a fastener in which the ribs embed themselves within a surface of a piece of material when the fastener is inserted to preclude rotation of the fastener while a threaded fastener is threaded into the threaded opening in the shaft thereof.